Recently the use of battery powered industrial material handling equipment, as opposed to internal combustion powered equipment, has increased. The primary reason for this trend is the increased concern about pollution, the increased cost and uncertain supply of LPG and similar fuels, as well as the increased safety inherent in electrical equipment.
The typical battery used in industrial material handling equipment, such as a lift truck, is made up of a multiplicity of lead cell batteries housed in a steel shell. The size, weight and voltage can vary with the power demands of the equipment, but the majority of such batteries will weigh in the range of 1,000 to 6,000 lbs.
Batteries used in mobile material handling equipment normally give 4 to 8 hours of service before requiring recharging Multiple shift operations, therefore, require capability of changing a discharged battery for a fully charged battery to keep the material handling equipment operating. As a normal charging cycle is between 8 to 16 hours, a minimum of three batteries and three battery changes are required to keep the equipment operating on a 24 hours basis.
With single shift operation, the batteries may be charged in the material handling equipment, but as the battery does require maintenance, removal of the battery from the equipment on a periodic basis is still required.
Historically, battery changing has been accomplished with overhead handling equipment, such as a crane, or a lifting beam attached to a lift truck. Overhead handling of the battery has distinct limitations. First, is the capital investment in either the crane or the lift truck. A second limitation is the intrinsic danger in the use of overhead equipment. Usually the battery changing is done by the material handling equipment operator, who is not a skilled crane operator.
Recent trends in the design of material handling equipment have put a premium on compactness of design. This has resulted in the placement of batteries in a location within the material handling equipment which precludes overhead handling of the battery. Thus, removal and replacement of the battery requires that the battery be slid laterally out of the battery compartment and then handled by overhead handling equipment or other means.
Manually operated devices, such as those shown in U.S. Pat. Nos. 3,122,244 and 3,259,365, have been proposed to remove batteries from material handling equipment. More recently, electromagnetic devices have also been used for this purpose. However, all of the battery removing devices, as used in the past, have had certain limitations in either removing the battery from the material handling equipment, or in transporting the battery to and from the recharging station.